In a liquid crystal display device which is one type of display device, since a liquid crystal display panel displaying an image is not luminous, an illumination device called a backlight unit is provided on the back surface side of the liquid crystal display panel (the opposite side to the display surface side of the liquid crystal display panel), the back surface of the liquid crystal display panel is illuminated by the backlight unit and thus a display operation is performed.
In the liquid crystal display device as described above, in order to reduce variations in brightness, it is necessary to uniformly illuminate an effective display region.
Hence, for example, in a direct type backlight unit, a light source is arranged in a region directly below a liquid crystal display panel (region opposite the back surface of the liquid crystal display panel), a diffusion plate is further arranged between the light source and the liquid crystal display panel and light generated by the light source is diffused by the diffusion plate, with the result that the light from the light source is spread over the entire effective display region (for example, see patent document 1).